1. Field of the Invention:
The present invention relates to moving sequence controlling apparatus for a plurality of machine tools, including industrial robots, and more particularly to a method and apparatus for recovering the normality of a moving sequence, which is suitable for automatically correcting a data table necessary for restarting and for judging what portion of a machine tool is displaying an abnormality in cases where an abnormality has occurred in a machine tool and a workstation has stopped.
2. Description of the Prior Art:
Recently, factory automation (FA) has come to be emphasized, and there has been a strong demand in the FA field for effecting efficient machining and assembling work by combining automatic machine tools, industrial robots, and the like.
When effecting cooperated operation by combining teaching playback-type robots and automatic machine tools, it has heretofore been necessary to compile a control program using interlocks between the various devices, and there has been a problem in that this work is extremely troublesome.
A method is known in which a parts-installing station using two robots is caused to operate cooperatively while effecting synchronous and exclusive control by means of interlocking signals, which was disclosed in "Application of a Mark flow Diagram to the Design of a Multi-Process Sequence Control System" in Report No. 1115 of the Lectures presented at the 19th Lecture Meeting of the Automatic Control Association (hereinafter referred to as Literature (1)) as well as in the "Proposal of a Station Controller (SCR) for Controlling a Workstation" in Report No. 1314 of the 22nd SICE Academic Lecture Meeting (hereinafter referred to as Literature (2)).
When an abnormality has occurred in a workstation controlled by the aforedescribed method and the workstation has stopped as a result, the operator must judge the condition of the trouble. Furthermore, in order to resume operation starting with the unit operation which had been in effect before the occurrence of the abnormality, there is a need to reset the internal condition of an operation management table (details of which will be described later) to the condition which had been in effect at that time. In this case, since each unit operation had been engaging or was engaged with an interlocking signal, it is difficult to judge regarding which operation No. the execution management status or operation status should be corrected. Particularly in the case of a unit operation in which two or more sync/excl steps have the operation No. as its execute stand-by operation No., i.e., in the case where a unit operation involves at least two sequences for executing the unit operation (said unit operation being hereafter referred to as a "junction operation"), it is difficult to reset the internal condition of the operation management table. For this reason, when an abnormality has occurred, much time is required in restarting the workstation. Also, when the portion needing alteration is mistaken, there is a danger of this leading to a reckless operation or possible damage to the equipment.
Additionally, in automated facilities where a large number of limit or proximity switches are used, the limit switches or the like are used to confirm the operation. However, since these limit switches or the like are physically operated, the level of their reliability is low. Moreover, when this type of switch fails, they have poor reproducibility.
For these reasons, in conventional automated facilities, when an abnormality has occurred in the facilities, there are problems in that it is difficult to identify the causes of the abnormality, and that, even if it is understood that a failed limit switch is the cause, it is quite troublesome to find out which limit switch is faulty.
To cope with this situtation, it is feasible to input fault-diagnosing data different from the controlling data. To do this, however, it is of course necessary to separately compile diagnosing data, and, moreover, it is necessary to change the diagnosing data as well when a change is made in the controlling data. Thus, there are numerous disadvantageous and troublesome aspects to such a procedure.